Processes and systems for using biomineral by-products as a fuel and for NOx removal at coal burning power plants

ABSTRACT

Processes and systems are provided that include introducing ammonia liberated from organic waste to a coal burner in a coal burning power plant, preferably for NO x  removal at the power plant. The ammonia is preferably either ammonia liberated upon drying a mixture of organic waste and coal combustion byproducts or ammonia liberated when organic waste is mixed with coal combustion by-products and one or more alkaline additives. Also provided are processes and systems of fueling a coal burner of a power plant with coal and either a dried mixture of organic waste and coal combustion by-products, or a mixture of organic waste, coal combustion by-products and one or more alkaline additives. The present invention is further directed to mixtures of either organic waste and coal combustion by-products, or mixtures of organic waste, coal combustion by-products and alkaline additives made by the processes of the present invention.

[0001] This application is a continuation-in-part of co-pendingapplication U.S. Ser. No. 09/839,112, the subject matter of which isincorporated by reference hereto.

FIELD OF THE INVENTION

[0002] The present invention is directed to processes and systems atcoal burning power plants, which include introducing ammonia liberatedfrom organic waste to a coal burner in the power plant.

[0003] The present invention is also directed to processes and systemsof fueling a coal burner of a power plant with coal and either a driedmixture of organic waste and one or more coal combustion by-products, ora mixture of organic waste, one or more coal combustion by-products, andoptionally one or more alkaline additives.

[0004] The present invention is further directed to dried mixtures oforganic waste and coal combustion by-products or mixtures of organicwaste, coal combustion byproducts and optional alkaline additives madeby the processes of the present invention.

BACKGROUND OF THE INVENTION

[0005] Mineral by-products have been used in stabilizing semi-solid,odorous organic waste through bulk drying, odor absorption, andgranulation (see e.g., U.S. Pat. Nos. 3,877,920 and 4,554,002). Inaddition, mineral materials including sand, diatomaceous earth, perlite,and various mineral reagent powders have been used in conjunction withfluidized heating, drying and burning of sludges and oily waste (seee.g., U.S. Pat. Nos. 4,159,682, 4,787,323, 4,970,803, 5,490,907).However, existing thermal dryers have ongoing problems with drying wastehigh in organics, particularly sewage sludges, in the waste sticking todryer surfaces, charring and producing burnt organic matter odors, andcatching on fire.

[0006] Organic waste has traditionally been disposed of by incineration,primarily in stand-alone plants designed for a particular waste. Wetwaste, such as dewatered sewage sludge filter cake, requiressupplemental fuel to initiate and sustain burning, and sludges are notself-burning until solids contents are greater than about 30%. Dryorganic waste such as paper and cardboard are net energy producers andmunicipal refuse incinerators that use these feedstocks are capable ofsignificant power generation. Likewise, dried animal manures likebroiler chicken litter, which contains sawdust that is used as bedding,can have a solids content in excess of 75% and can be incinerated without supplemental fuel. Processes of more efficiently disposing oforganic waste are desirable.

[0007] NO_(x) created during the burning of coal can react with volatileorganic compounds in the presence of heat and sunlight to form ozone.Gaseous ammonia, in the form of commercial anhydrous ammonia and itsmain derivative, urea, are currently used in treating fossil fuelcombustion exhausts for NO_(x) removal. This is a very expensiveprocess, however. Therefore, inexpensive sources of ammonia or methodsof recycling ammonia are desirable.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to processes and systems atcoal burning power plants, which include introducing ammonia liberatedfrom organic waste to a coal burner in the power plant. The ammonia maybe ammonia that is liberated upon drying a mixture of organic waste andone or more coal combustion byproducts, preferably having a pH of atleast 9.5, or the ammonia may be ammonia that is liberated when organicwaste is mixed with one or more coal combustion byproducts, such as flyash, and one or more alkaline additives. Preferably, the presentprocesses and systems remove NO_(x) at the power plant. The liberatedammonia that is introduced to the coal burner by the present processesand systems, may supplement commercial anhydrous ammonia or urea addedto the coal burner, for example, for NO_(x) removal.

[0009] The present invention is also directed to processes and systemsof fueling a coal burner of a power plant with coal and either a driedmixture of organic waste and coal combustion by-products, or a mixtureof organic waste, coal combustion by-products and optionally alkalineadditives. The coal is preferably pulverized coal. In this embodiment,the dried mixture of organic waste and coal combustion by-products orthe mixture of organic waste, coal combustion by-products and alkalineadditives, is optionally a source of supplemental fuel to the coalburner.

[0010] The present invention is further directed to dried mixtures oforganic waste and coal combustion by-products made by the processes ofthe present invention, and to mixtures of organic waste, coal combustionby-products and optional alkaline additives made by the processes of thepresent invention. The mixtures of the present invention optionallyadditionally contain lime.

[0011] Non-limiting examples of organic waste used in the process of thepresent invention include, but are not limited to, dewatered sewagesludge filter cake, various animal manures, pulp and paper waste,fermentation waste, shredded paper and cardboard, food waste (such asfood processing waste), and other organic industrial waste and mixturesthereof.

[0012] Certain embodiments of the present invention do not requiredrying, such as in the case of organic wastes that are already dry.However, in embodiments that include drying, a mixture of organic wasteand one or more coal combustion byproducts (optionally including one ormore alkaline additives) is dried to preferably at least 50% solids,more preferably at least 75% solids, even more preferably at least 90%solids. The drying preferably takes place in a direct or indirect dryerand preferably uses waste heat from the power plant.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a flow diagram of an organic waste drying and fuel feedsystem according to an embodiment of the present processes and systems.

[0014]FIG. 2 is a flow diagram of the organic waste mixing and fuel feedsystem of another embodiment of the present processes and systems.

DETAILED DESCRIPTION

[0015] The present invention will now be described in detail with regardto specific preferred embodiments of the invention, it being understoodthat these embodiments are intended only as illustrative examples andthe invention is not to be limited thereto.

[0016] Coal-fired power plants must deal with the problems of NO_(x)removal from exhaust gases, renewable fossil fuel power generation,odor, and dissipation of waste energy. The present inventors havearrived at processes and systems that advantageously synergisticallyincorporate processes of releasing ammonia from organic waste andreducing NO_(x) emissions at a power plant, which utilizes waste(including for example, heat and/or by-products) from each process inthe other process.

[0017] Organic waste produces ammonia under certain conditions, whichexcess ammonia may be used for example, to reduce NO_(x) emissions at apower plant. The present invention provides processes at coal burningpower plants, which include supplying liberated ammonia from wastetreatment to a coal burning power plant, to preferably remove NO_(x)from the plant.

[0018] Combining organic waste with one or more coal-combustionby-products and drying the organic waste is a method by which ammoniamay be released from the waste. Drying waste, which typically containsfrom about 12 to about 75% solids, depending on waste type, is energyintensive. In the present invention, in which drying is conducted at apower plant, waste heat from the plant can be used as a heat source indrying the organic waste. Power plants produce several types of wasteheat: hot exhaust gases, hot ash, steam and hot water. These sources arereadily available for organic waste drying. Whereas, if the power plantdid not have a recipient for the excess heat, the heat would have to befurther treated, e.g., excess steam or hot water must be cooled beforethey can be discharged back into the environment. The present inventionreduces or eliminates the excess cooling step in present power plantsbecause the heat is used directly in the treatment of organic waste.

[0019] According to an embodiment of the invention, processes areprovided that include mixing organic waste with one or more coalcombustion by-products (for example from a coal burner or furnace of thepower plant or from any other source known to those skilled in the art)to form an organic waste-coal combustion byproduct mixture, preferablyhaving a pH of at least 9.5, even more preferably having a pH of atleast 10. As set forth in a U.S. Provisional Application filed on Apr.20 2001 entitled “Methods for Controlling Ignitability of Organic Wastewith Mineral By-Products”, which is hereby incorporated by referenceherein in its entirety, the addition of coal combustion by-product toorganic waste prior to drying is preferred in that it may serve toprevent fires and explosions that are common in conventional organicmaterials drying.

[0020] The next step in this embodiment includes drying with heat theorganic waste-coal combustion by-product mixture to preferably at least50% solids, more preferably at least 75% solids, even more preferably atleast 90% solids. According to an embodiment of the invention, themixture is dried to at least 95% solids, preferably as near 100% solidsas possible, thus forming a “dried organic waste-coal combustionby-product mixture.” The drying causes ammonia to be liberated from theorganic waste.

[0021] According to certain embodiments the organic waste issufficiently dry without a drying step that no drying step is requiredfor ammonia to be liberated from the organic waste. For example, somepoultry manures include 70% or more solids. Accordingly, the presentinvention includes mixing organic waste with one or more coal combustionby-products to form an organic waste-coal combustion byproduct mixture,which releases ammonia from the organic waste upon mixing.

[0022] The liberated ammonia is then introduced into a coal burner of acoal burning power plant, preferably for NO_(x) removal. Alternatively,the ammonia may be introduced to the coal burner for a purpose otherthan NO_(x) removal that would be apparent to those skilled in the art.

[0023] Under certain conditions, such as at pH conditions greater thanabout 9.5 or greater than about 10.0, and under dry and hot conditions,the ammonia in these wastes is converted to free gaseous ammonia.Organic wastes that are particularly suitable for use in this embodimentof the present invention contain ammonia that is liberated under certainconditions (such as when the organic waste is in a mixture having pH'sabove about 9.5 or above about 10.0).

[0024] Examples of organic waste that may be used in accordance with thepresent invention include, but are not limited to, sewage sludges, suchas dewatered sewage sludge filter cake; various animal manures; pulp andpaper waste; shredded paper and cardboard; fermentation waste; foodwaste; and other industrial organic waste as would be apparent to thoseskilled in the art. In particular, organic waste such as sewage sludges,animal manures, fermentation biomass, and some food waste are high inprotein and ammonia, and thus, are preferred in embodiments of thepresent invention that involves liberating ammonia from the waste. Whatis meant by the named types of waste would be readily apparent to thoseskilled in the art.

[0025] Coal combustion by-products may include one or more by-productsfrom a coal burner (preferably from the coal burner from which NO_(x)may be removed by the processes of the present invention) or coalcombustion by-products from other sources. Examples of coal combustionby-products according to the present invention include, but are notlimited to the following by-products: fly ash, bottom ash, fluidized bedash, flue gas desulfurization by-products, lime, calcium hydroxide, andcalcium carbonate, and combinations or mixtures thereof. In particular,preferred coal combustion by-products include alkaline mineralby-products. As set forth herein, certain embodiments of the presentinvention include one or more alkaline mineral by-products in additionto the one or more coal combustion by-products that may include alkalinemineral by-products.

[0026] Fly ashes are the mineral residues of burning coal forelectricity generation. Fly ash can be collected from the smoke stack ofa burner (or furnace) by bag houses, electrostatic precipitators, or indown washes. Fly ashes have variable fineness, solids content, andchemical composition. Preferable fly ashes for use in the presentinvention are dry ashes. The chemical composition of ash depends on thetype of coal that is burned. For example, coals from the western U.S.are typically high in calcium and thus, may contain a higher limecontent than coals from the eastern U.S. Eastern coals are often higherin pyrite (FeS₂), which oxidizes on burning to SO₂, producing an acidicfly ash. Fly ashes are high in silicon, and are often in the form of aspherical glass. Some fly ashes are high in residual carbon in the formof charcoal and these are effective in absorbing biosolids odors.Preferably, odors of the present processes and systems are keptsufficiently low that the present processes and systems are notunacceptable to plant operators, or others working at or near the plant.Thus, the amount of coal combustion by-products (or other ingredients tothe mixture) that control odor level, such as fly ash, for example, ispreferably adjusted to as to maintain an acceptable odor level.

[0027] Fluidized bed ash (FBA) refers to ash that is produced in afluidized bed burner, in which a mixture of pulverized coal andlimestone is burnt as a suspended, i.e., fluid, mass, the purpose of thelimestone being to react with SO₂ produced from the oxidation of pyritein the coal.

[0028] Flue gas desulfurization by-product (FGD) is a general termreferring to a range of products formed when lime or limestone are usedto remove SO₂ produced from the oxidation of pyrite in the coal. FGDsmay be pure gypsum (CaSO₄.2H₂O), anhydrite (CaSO₄), or CaSO₃. FGDs mayalso contain fly ash, unburnt carbon and unreacted lime.

[0029] Lime (CaO), calcium hydroxide (Ca(OH)₂), and limestone, ascalcite (CaCO₃) or dolomite (CaMg(CO₃), limestone, cement kiln dust,lime kiln dust and FGD are alkaline by-products familiar to thoseskilled in the art, many of which are commercially available.

[0030] An embodiment of the processes of the present invention isdepicted in FIG. 1. As shown in FIG. 1, organic waste from source I andone or more coal combustion by-products from source 2 are added to amixer 3 in which the organic waste and coal combustion by-products aremixed with one another to form an organic waste-coal combustionby-product mixture, preferably having a pH of at least about 9.5, evenmore preferably at least 10. According to one embodiment of the presentinvention, the mixing additionally includes mixing lime with the organicwaste and coal combustion by-products. The organic waste-coal combustionby-product mixture is then transferred to a dryer 4. Alternatively, theorganic waste and coal combustion by-products are mixed directly in thedryer 4 eliminating the need for a separate mixer 3.

[0031] Next, according to the embodiment depicted in FIG. 1, the dryer 4dries the organic waste-coal combustion by-product mixture to preferablyat least 50% solids, more preferably at least 75% solids, even morepreferably at least 90% solids, forming a dried organic waste-coalcombustion by-product mixture. However, certain embodiments of thepresent invention do not require drying, such as in the case of organicwastes that are already sufficiently dry that mixing alone causesrelease of ammonia from the organic waste.

[0032] Commercial dryers that may be used to accomplish drying, areavailable in two forms, direct and indirect. A dryer according to thepresent invention may include at least one direct dryer or indirectdryer. Direct dryers use heated air in direct contact with the organicwaste. According to one embodiment, exhaust stack gases from the powerplant are used directly, or waste steam, hot ash, or hot water from thepower plant is used with a heat exchanger to heat air for drying.

[0033] Alternatively, indirect dryers may be used for drying, which heatmetal surfaces that come in contact with the organic waste. In anexample of this embodiment, waste steam or hot water from the powerplant is used to heat the drying surfaces via a heat exchanger in whichthe waste steam or water is used to heat oil, the fluid normally used inindirect dryers. Non-limiting examples of suitable dryers according tothe present invention include direct concurrent flow dryers, horizontalsingle, double and triple pass indirect dryers, and vertical counterflow rotating disk indirect dryers.

[0034] The heat for the drying may include using waste heat 5 from thecoal burning power plant in addition to or instead of heat from anothersource, such as a steam turbine 11 in the embodiment depicted in FIG. 1.As indicated above, the power plant waste heat 5 used in the drying maybe in the form of hot exhaust gases, hot ash, steam or hot water, forexample, and may be used with direct or indirect dryers.

[0035] When hot ash is a source of heat for the drying, hot ash may beprovided from a power plant, for example from the boiler of a powerplant. Either the heat of the hot ash may be used via some sort of dryerand/or heat exchanger to heat the mixture, and/or hot ash may be addeddirectly to the mixture to dry it. That is, no heat exchanger isnecessary. For example, hot ash from a silo or other source may be mixedin a mixer with the organic waste mixture and through tumbling, heatfrom the hot ash dries the mixture. The hot ash may be in any form knownto those skilled in the art.

[0036] Drying the mixture of organic waste and coal combustionby-products, preferably at a pH above 9.5 or 10, preferably causesammonia to be liberated from the organic waste. The liberated ammonia ofthis embodiment is introduced as shown in stream 7, into a coal burner6.

[0037] The liberated ammonia that is introduced to the coal burner bythe present processes and systems, may supplement commercial anhydrousammonia or urea added to the coal burner for any purpose, such as NO_(x)removal. The amount of ammonia or urea may vary depending, for example,on the amount of ammonia or urea needed in order to reduce the NO_(x)emissions of a particular power plant to a desired (or required) level.The amount of ammonia or urea to be introduced to the coal burner may bedetermined by those skilled in the art.

[0038] In some embodiments, the mixture of organic waste and coalcombustion byproducts resulting from the present processes may notproduce ammonia. In these embodiments, the mixture may be useful forother purposes, for example as a fuel source or soil additive.

[0039] Drying may produce exhaust gases, in addition to the ammonia anddried organic waste-coal combustion by-product mixture. According to anembodiment of the present invention, the process includes reactingscavenged exhaust gases from the drying step with at least one reactivematerial to decrease the amount of polutant gases, such as CO₂, SO₂and/or SO₃ in the exhaust gases, preferably decreasing emissions fromthe drying step. Examples of suitable reactive materials would beapparent to those skilled in the art upon reading the presentdisclosure. Such reactive materials may include, for example, Ca(OH)₂.

[0040] An embodiment of the present invention includes a process wherethe coal combustion by-product preferably includes an alkaline mineralby-product and the drying step produces a further by-product. Thus, anembodiment includes mixing organic waste with at least one coalcombustion by-product, which preferably includes at least one alkalineby-product, to form an organic waste-coal combustion by-product mixtureand at least one further by-product. Another embodiment includes mixingorganic waste with at least one coal combustion by-product, whichpreferably includes at least one alkaline by-product, to form an organicwaste-coal combustion by-product mixture, which is then dried with heatto at least 50% solids, to form a dried organic waste-coal combustionby-product mixture and at least one further by-product.

[0041] A further embodiment of the present invention includes furtherby-products produced these processes. The further by-products may beuseful, for example, as soil additives that may replace or be added inaddition to agricultural limestone, for example, to neutralize soilacidity.

[0042] Another embodiment of the present invention includes thepreferably dried, organic waste-coal combustion by-product mixtureformed by the above-described processes. This mixture may be added to acoal burner of a power plant as depicted for example as feed stream 8 inFIG. 1. A preferred embodiment includes forming a dried organicwaste-coal combustion by-product mixture by a process that includesmixing organic waste with coal combustion by-products to form an organicwaste-coal combustion by-product mixture, and drying the organicwaste-coal combustion by-product mixture to at least 50% solids,preferably at least 75% solids, even more preferably at least 90%solids. The mixture may be used for example, as a soil additive or as afeed-stock to another process.

[0043] The processes of producing organic waste-coal combustionby-product mixture of the present invention do not necessarily releaseammonia from the organic waste. For example, according to an embodimentof the invention, the coal combustion by-product is non-alkaline flyash, which is mixed with organic waste to form an organicwaste-non-alkaline fly ash mixture that is then optionally dried. Thedried organic waste-non-alkaline fly ash mixture may be used for variouspurposes, for example, to control burning at the power plant and/or tocontrol odors.

[0044] A further embodiment of the present invention includes feedingthe (preferably dried) organic waste-coal combustion by-product mixtureto a coal burner, preferably as supplemental fuel, along with coal. Theorganic waste-coal combustion by-product mixture may be suitable as asupplemental fuel because its caloric content is similar to that ofcoal. For example, undigested sewage sludge has a caloric contentsimilar to that of coal, approximately 10,000 BTU per pound. The driedorganic waste-coal combustion by-product mixture is preferably mixedwith the coal prior to being fed to the coal burner. Preferably, thecoal is pulverized coal.

[0045] A further embodiment of the present invention includes methods ofchanging the physical characteristics of organic wastes to be morecompatible with pulverized coal. Organic wastes that have solidscontents of 50% or greater have much lower densities than coal. They mayalso have to undergo additional costly processing, such aspelletization, before they can be mixed with coal and burned. Themethods of the present invention include mixing organic waste with oneor more mineral additives such as one or more coal combustionby-products, or one or more alkaline additives or combinations thereofto form organic waste mixtures having densities that are more similar tocoal than the organic wastes alone. In addition, mixtures of organicwastes and mineral additives have granular characteristics that make themixtures more physically compatible with coal. Also included in thisembodiment are organic waste mixtures that exhibit an improvedcompatibility with pulverized coal, preferably formed by mixing organicwaste with one or more mineral additives, such as one or more coalcombustion by-products, or one or more alkaline additives orcombinations thereof.

[0046] An example of this embodiment is also depicted in FIG. 1.According to FIG. 1, the preferably dried, organic waste-coal combustionby-product mixture leaves the dryer 4 and is carried in stream 8 to thecoal feed 9 where the coal feed is mixed with the dried organicwaste-coal combustion by-product mixture prior to being introduced tothe coal burner 6.

[0047] The present invention is further directed to systems including acoal burner of a power plant, a coal feed supplying coal to the coalburner, and an ammonia feed to the coal burner. The ammonia feedpreferably includes ammonia liberated upon drying an organic waste-coalcombustion by product mixture to at least 50% solids The steps involvedin these systems, such as mixing and drying the organic waste, and theingredients of the system, such as the organic waste and coal combustionbyproducts, are as described above with regard to the processes of thepresent invention. According to a preferred embodiment, the coal feedincludes coal and a dried mixture of organic waste and one or more coalcombustion by-products. Preferably, the coal is pulverized coal.According to a further embodiment, the coal and the dried mixture oforganic waste and coal combustion by-product are mixed and thenpulverized.

[0048] A further embodiment of the invention is directed to systemsincluding a coal burner of a power plant, and a feed of an organicwaste-coal combustion by-product mixture to the coal burner, where thefeed includes organic waste and one or more coal combustion by-productsmixed together and optionally dried. According to a preferredembodiment, the feed of organic waste-coal combustion by-product mixturefurther includes coal. Preferably, the coal is pulverized coal.According to a further embodiment, the coal and the dried mixture oforganic waste and coal combustion by-product are mixed and thenpulverized.

[0049] Other systems of the present invention include a coal burner of acoal burning power plant; an ammonia feed to the coal burner, whichpreferably includes ammonia liberated upon mixing an organic waste andone or more coal combustion by-products and/or drying such a mixture toat least 50% solids; and a coal feed supplying coal to the coal burner,which coal feed includes coal and the mixture of organic waste and coalcombustion by-product.

[0050] Under certain conditions, when organic waste is mixed with one ormore coal combustion by-products (such as fly ash), and optionally oneor more alkaline additives, ammonia in the organic waste may beconverted to free gaseous ammonia, without the need for drying themixture.

[0051] Therefore, according to another embodiment of the invention,processes are provided that include mixing organic waste with one ormore coal combustion by-products (for example from a coal burner orfurnace of the power plant or from any other source known to thoseskilled in the art) and optionally one or more alkaline additives,preferably causing ammonia to be liberated from the organic waste. Theliberated ammonia of this embodiment is introduced into a coal burner ofa coal burning power plant. As set forth above with regard to otherembodiments of the invention, the liberated ammonia is then preferablyintroduced to the coal burner. Organic waste and the one or more coalcombustion by-products according to these embodiments are as set forthabove with regard to other embodiments of the present invention.Preferably, the one or more coal combustion by-products of thisembodiment include at least one of fly ash, bottom ash and fluidized bedash, more preferably fly ash.

[0052] Alkaline additives according to the present invention, includebut are not limited to lime (CaO), calcium hydroxide (Ca(OH)₂), andlimestone, such as calcite (CaCO₃) or dolomite (CaMg(CO₃), cement kilndust and lime kiln dust. Preferably, the alkaline additives are selectedin kind and amount so as to be sufficient to cause ammonia to bereleased from organic waste upon mixing with the organic waste and oneor more mineral by-products, or upon heating the organic waste and oneor more mineral by-products.

[0053] An embodiment of the processes of the present invention isdepicted in FIG. 2. As shown in FIG. 2, organic waste from source 12,coal combustion by-products from source 13, and one or more alkalineadditives from source 14 are added to a mixer 15 in which the organicwaste, coal combustion by-products and alkaline additives are mixed withone another to form an organic waste/coal combustionby-products/alkaline additive mixture.

[0054] The organic waste/coal combustion by-products/alkaline additivemixture may optionally be transferred from the mixer to a dryer (notshown) to dry the mixture such that it preferably contains at least 50%solids, more preferably at least 75% solids, even more preferably atleast 90% solids, forming a dried organic waste-coal combustionby-product mixture. Dryers and heat sources that may be used toaccomplish such drying, are as described above.

[0055] Mixing the organic waste, coal combustion by-products andalkaline additives preferably causes ammonia to be liberated from theorganic waste. In embodiments, where ammonia is liberated from theorganic waste, the liberated ammonia is preferably fed into the coalburner, for example in FIG. 2 ammonia is introduced as shown in stream16, into a coal burner 18.

[0056] The liberated ammonia that is introduced to the coal burner 18 bythe present processes, may supplement commercial anhydrous ammonia orurea added to the coal burner for any purpose, such as for NO_(x)removal. Alternatively, the ammonia may be introduced to the coal burnerfor a purpose other than NO_(x) removal that would be apparent to thoseskilled in the art. The amount of ammonia or urea may vary depending,for example, on the amount of ammonia or urea needed in order to reducethe NO_(x) emissions of a particular power plant to a desired (orrequired) level. The amount of ammonia or urea to be introduced to thecoal burner for NO_(x) removal may be determined by those skilled in theart.

[0057] Exhaust gases (other than ammonia, such as CO₂, SO₂, and SO₃) maybe produced by mixing the organic waste, coal combustion by-products andalkaline additives or by drying the resulting mixture. According to anembodiment of the present invention, a process is provided that includesreacting scavenged exhaust gases from a mixing or drying step with atleast one reactive material to decrease the amount of polutant gases,such as CO₂, and other exhaust gases, such as SO₂ and SO₃, in theexhaust gases and thereby decrease any emissions from the mixing ordrying steps. Examples of suitable reactive materials would be apparentto those skilled in the art upon reading the present disclosure. Suchreactive materials may include, for example, Ca(OH)₂.

[0058] According to an embodiment of the invention, the coal combustionbyproducts mixed with organic waste and alkaline additives may beprovided in whole or in part from a burner or furnace (such as coalburner 18 of FIG. 2).

[0059] Another embodiment of the present invention includes an organicwaste/coal combustion by-products/alkaline additive by-product mixtureformed by the above-described processes. This mixture may be used forexample, as a soil additive or as a feed-stock to another process or maybe added to a coal burner of a power plant as depicted for example asfeed stream 17 in FIG. 2. The mixture may also be used to control odorand/or burning in the plant. A preferred embodiment includes forming aorganic waste/coal combustion by-products/alkaline additive by-productmixture by a process that includes mixing organic waste with coalcombustion by-products and at least one alkaline additive to form anorganic waste/coal combustion byproducts/alkaline additive by-productmixture. The mixture is then optionally dried to at least 50% solids,preferably at least 75% solids, even more preferably at least 90%solids.

[0060] Another embodiment of the present invention includes feeding theorganic waste/coal combustion by-products/alkaline mixture to a coalburner, preferably as supplemental fuel, along with coal. The organicwaste/coal combustion byproducts/alkaline additive by-product mixturemay be suitable as a supplemental fuel because its caloric content issimilar to that of coal. The organic waste/coal combustionby-products/alkaline additive by-product mixture is preferably mixedwith the coal prior to being fed to the coal burner. Preferably, thecoal is pulverized coal.

[0061] An example of this embodiment is also depicted in FIG. 2.According to FIG. 2, the organic waste/coal combustionby-products/alkaline additive by-product mixture leaves the mixer 15 (orthe dryer—not shown) and is carried in stream 17 to the coal feed 19where the coal feed is mixed with the organic waste/coal combustionby-products/alkaline additives by-product mixture before beingintroduced to the coal burner 18.

[0062] Further embodiments of the present invention include feeding anorganic waste/coal combustion by-products mixture that does notnecessarily include alkaline additives to a coal burner, preferably assupplemental fuel, along with coal. In these embodiments, the mixturemay include one or more alkaline or non-alkaline additives or noadditives at all. By way of example, the present invention includes aprocess that includes mixing organic waste (such as pulp and paperwaste) with one or more coal combustion by-products (such asnon-alkaline fly ash), and optionally one or more non-alkaline additivesthat would be apparent to those skilled in the art, and feeding theorganic waste/coal combustion by-product/non-alkaline additive mixtureto a coal burner of a coal burning power plant. The organic waste/coalcombustion by-products mixture is preferably mixed with the coal priorto being fed to the coal burner. Preferably, the coal is pulverizedcoal.

[0063] A preferred embodiment of the present invention includes aprocess that includes mixing organic waste with coal combustionby-products and alkaline additives, thus producing ammonia, andintroducing liberated ammonia from the organic waste into the burner,preferably for NO_(x) removal. Preferably the organic waste/coalcombustion by-products/alkaline additive by-product mixture is mixedwith pulverized coal as supplemental fuel for the coal burner.

[0064] In an embodiment of the invention, lime is added to organic wasteto achieve a pH preferably greater than 9.5, more preferably greaterthan 10, and to aid in drying to high solids, in embodiments where theorganic waste is dried. Hot exhaust gases, hot ash, steam, hot water, ora combination of these heat sources scavenged from the power plant maybe used to dry, in a direct or indirect dryer, the coal combustionby-products-organic waste mixture to a solids content of at least 95%,preferably near 100%. Exhaust gases from the dryer, containing freeammonia from the organic waste, are piped into the coal burner tosupplement ammonia addition to the coal burner for NO_(x) removal.Preferably, the dried mixture is conveyed to the coal feed area of thepower plant and mixed with coal prior to or after coal pulverization toserve as a supplemental fuel source. Alternatively, the dried mixturecan be used as a soil additive.

[0065] The present invention is further directed to systems including acoal burner of a power plant, a coal feed supplying coal to the coalburner, and an ammonia feed to the coal burner. The ammonia feedpreferably includes ammonia liberated from organic waste upon mixingorganic waste, coal combustion by-products and one or more alkalineadditives. The step(s) involved in these systems, such as mixing andoptionally drying the organic waste, and the ingredients of the system,such as the organic waste, coal combustion by-products and alkalineadditive(s), are as described above with regard to the processes of thepresent invention. According to a preferred embodiment, the coal feedincludes coal and a mixture of organic waste, coal combustionby-products and alkaline additive(s). Preferably, the coal is pulverizedcoal. According to a further embodiment, the coal and the mixture oforganic waste, coal combustion by-products and alkaline additive(s) aremixed and then pulverized.

[0066] A further embodiment of the invention is directed to systemsincluding a coal burner of a power plant, and a feed of an organicwaste/coal combustion by-product/alkaline additive mixture to the coalburner, where the feed includes organic waste, coal combustionby-products and one or more alkaline additives mixed together. Accordingto a preferred embodiment, the feed of organic waste/coal combustionby-products/ alkaline additive by-product mixture further includes coal.Preferably, the coal is pulverized coal. According to a furtherembodiment, the coal and the organic waste/coal combustionby-products/alkaline additive by-product mixture are mixed and thenpulverized.

[0067] Other systems of the present invention include a coal burner of acoal burning power plant, an ammonia feed to the coal burner, whichpreferably includes ammonia liberated upon mixing organic waste, coalcombustion by-products, and one or more alkaline additives; and a coalfeed supplying coal to the coal burner, which coal feed includes coaland the organic waste/coal combustion by-products/ alkaline additiveby-product mixture.

[0068] The present invention will now be described in detail withrespect to showing how certain specific representative embodimentsthereof can be made, the materials, apparatus and process steps beingunderstood as examples that are intended to be illustrative only. Inparticular, the invention is not intended to be limited to theprocesses, materials, conditions, process parameters, apparatus and thelike specifically recited herein.

EXAMPLES Example 1

[0069] An anaerobically digested sewage sludge is mixed with spentfluidized bed coal ash containing 10% by weight CaO at a coal-firedpower plant burning high-S coal. Fly ash and sludge are mixed to form amixture having a pH of 12 or above. The mixture is introduced into avertical counter-current indirect dryer with rotating plates in whichthe rotating plates are heated with excess steam from the power plant.The sludge contains 2% by dry weight of ammonia. Due to the high pH,ammonia is released from the sludge in the dryer and is exhausted andpiped to the coal burner to supplement anhydrous ammonia or urea usedfor NO_(x) control from the coal burner. The mixture is dried to >95%solids.

[0070] The dried mixture is conveyed by covered belt to the coal feedhopper where it is further mixed with coal. This mixture is fed into thecoal pulverizer and thence into the burner. The mixing of high CaO flyash with sludge results in the formation of Ca(OH)₂. The concurrentintroduction of exhaust air from the plant results in carbonation of theCa(OH)₂ to form CaCO₃. The presence of CaCO₃ in the dried mixturereduces the amount of commercial limestone required by the power plantfor sulfur removal.

Example 2

[0071] An anaerobically digested sewage sludge is mixed with fly ash(containing CaO) and lime kiln dust at a coal-fired power plant burninghigh-S coal. The resulting mixture has a pH of 10 or above. Ammonia isreleased from the sludge in the mixer and is exhausted and piped to thecoal burner to supplement anhydrous ammonia or urea used for NO_(x)control from the coal burner.

[0072] The mixture is conveyed by covered belt to the coal feed hopperwhere it is further mixed with coal. This mixture is fed into the coalpulverizer and thence into the burner. The mixing of high CaO fly ashwith sludge results in the formation of Ca(OH)₂. CaO in the lime kilndust also results in formation of Ca(OH)₂. The concurrent introductionof exhaust air from the plant results in carbonation of the Ca(OH)₂ toform CaCO₃. The presence of CaCO₃ in the dried mixture reduces theamount of commercial limestone required by the power plant for sulfurremoval. In addition, CO₂ in exhaust gases is sequestered by a reactionof Ca(OH)₂to form CaCO₃. In a further embodiment SO₂ and SO₃ in theexhaust air from the plant are sequestered by reaction with Ca(OH)₂ toform CaSO₃ and CaSO₄.

[0073] Processes and systems of the present invention are advantageousover previously known processes because enabling the release of ammoniafrom organic waste at a power plant allows the ammonia in the organicwaste to be utilized for example, for NO_(x) removal, while takingadvantage of the fuel value of the organic waste. The present processesand systems also provide flexibility in resource utilization in that theorganic waste mixtures formed by the present processes can be usedeither as fuel or as a separate product that can be applied to land as asoil additive.

[0074] While the present invention is described with respect toparticular examples and preferred embodiments, it is understood that thepresent invention is not limited to these examples and embodiments. Inparticular, the present invention is not limited to the particular typesof waste or by-products. Additionally, the components of the processesof the present invention are not limited to those described above ordepicted in FIGS. 1 and 2. For example, the processes of the presentinvention are not limited to a single dryer or a single coal burner andadditional components may be added such as a sorbant 10 in FIG. 1, heatexchangers, belts, and the like.

[0075] The present invention as claimed therefore, includes variationsfrom the particular examples and preferred embodiments described herein,as will be apparent to one of skill in the art.

We claim:
 1. A coal burner feedstock comprising coal and a mixture oforganic waste/coal combustion by-product/alkaline additive formed by aprocess comprising mixing organic waste, one or more coal combustionby-products, and one or more alkaline additives to form an organicwaste/coal combustion byproduct/alkaline additive mixture having asolids content of at least 50%; and combining the organic waste/coalcombustion by-product/alkaline additive mixture with coal.
 2. Thefeedstock of claim 1, wherein said organic waste/coal combustionbyproduct/alkaline additive mixture has a solids content of at least75%.
 3. The feedstock of claim 1, wherein said organic waste/coalcombustion byproduct/alkaline additive mixture has a solids content ofat least 90%.
 4. The feedstock of claim 1, wherein said coal comprisespulverized coal.
 5. The feedstock of claim 1, comprising one or morecoal combustion byproducts selected from the group consisting of flyash, fluidized bed ash, flue gas desulfurization by-products andmixtures thereof.
 6. The feedstock of claim 5, wherein said coalcombustion by-product comprises fly ash.
 7. The feedstock of claim 1,wherein said alkaline additive is selected from the group consisting oflime, calcium hydroxide, calcium carbonate, cement kiln dust, lime kilndust and mixtures thereof.
 8. The feedstock of claim 7, wherein saidalkaline additive comprises lime.
 9. The feedstock of claim 7, whereinsaid alkaline additive comprises cement kiln dust.
 10. The feedstock ofclaim 7, wherein said alkaline additive comprises lime kiln dust. 11.The feedstock of claim 1, wherein said organic waste comprises wasteselected from the group consisting of sewage sludges, animal manures,pulp and paper waste, fermentation waste, food waste, paper andcardboard, and other industrial organic waste.
 12. A coal burnerfeedstock comprising coal and a mixture of organic waste/coal combustionby-product formed by a process comprising mixing organic waste and oneor more coal combustion by-products to form an organic waste/coalcombustion by-product mixture having a solids content of at least 50%;and combining the organic waste/coal combustion by-product mixture withcoal.
 13. The process of claim 12, wherein said organic waste/coalcombustion byproduct mixture has a solids content of at least 75%. 14.The process of claim 12, wherein said organic waste/coal combustionbyproduct mixture has a solids content of at least 90%.
 15. The processof claim 12, wherein said coal comprises pulverized coal.
 16. Theprocess of claim 12, comprising one or more coal combustion byproductsselected from the group consisting of fly ash, fluidized bed ash, fluegas desulfurization by-products and mixtures thereof.
 17. The process ofclaim 16, wherein said coal combustion by-product comprises fly ash. 18.The process of claim 12, wherein said organic waste comprises wasteselected from the group consisting of sewage sludges, animal manures,pulp and paper waste, fermentation waste, food waste, paper andcardboard, and other industrial organic waste.
 19. A coal burner feedstock comprising coal and an organic waste/coal combustion by-productmixture, wherein said organic waste/coal combustion by-product mixturehas a solids content of at least 50%.
 20. The feedstock of claim 19,wherein said organic waste/coal combustion by-product mixture has asolids content of at least 75%.
 21. The feedstock of claim 19, whereinsaid organic waste/coal combustion by-product mixture has a solidscontent of at least 90%.
 22. The feedstock of claim 19, wherein saidcoal comprises pulverized coal
 23. The feedstock of claim 19, comprisingone or more coal combustion by-products selected from the groupconsisting of fly ash, fluidized bed ash, flue gas desulfurizationby-products and mixtures thereof.
 24. The feedstock of claim 23, whereinsaid coal combustion by-product comprises fly ash.
 25. The feedstock ofclaim 19, wherein said organic waste comprises waste selected from thegroup consisting of sewage sludges, animal manures, pulp and paperwaste, fermentation waste, food waste, paper and cardboard, and otherindustrial organic waste.
 26. The feedstock of claim 19, furthercomprising an alkaline additive selected from the group consisting oflime, calcium hydroxide, calcium carbonate, cement kiln dust, lime kilndust and mixtures thereof.
 27. The feedstock of claim 26, wherein saidalkaline additive comprises lime.
 28. The feedstock of claim 26, whereinsaid alkaline additive comprises cement kiln dust.
 29. The feedstock ofclaim 26, wherein said alkaline additive comprises lime kiln dust.